“One of the issues that Numbers USA is most concerned about is the way that immigration is driving so much destruction of the environment and farmland in this country,” Roy Beck, CEO of Numbers USA, told The Daily Caller News Foundation.

“The two big reasons we fight to bring immigration numbers are to protect the vulnerable American workers and the open space and natural habitat and farmland of the American people. We’re protecting them from explosive population growth caused by immigration,” Beck said.

Beck stands apart from many of today’s prominent environmental groups on the immigration issue.

Now, the Sierra Club has come out against President Donald Trump’s proposed U.S.-Mexico border wall, and the group supports a path to citizenship for illegal immigrants. The club lost members in 2013 when it came out as pro-immigration.

“A real focus on immigration solutions would include humane, sensible measures to address the root causes of migration,” the Sierra Club’s Dan Mills said in a statement on news Attorney General Jeff Sessions would tour the border in April.

“Instead, the Trump administration, and Mr. Sessions, are set on throwing good taxpayer money after bad on a boondoggle of a wall that will only cause greater harm to families and wildlife along the border, while failing as immigration policy,” Mills said.

Beck, on the other hand, blames population growth, including immigration, for “the vast majority of the loss of natural habitat in America.”

“The Census Bureau data shows that the majority of immigrants live in suburbs and the outer edges of cities. They very much drive the need for more roads, more schools, more everything,” Beck said.

Since, U.S. population growth is mainly driven by immigration, Beck thinks ignoring that issue on Earth Day could doom the environmental movement.

“Pew projections suggest that over 100 million people will be added to the U.S. population over the next 50 years,” Beck said. “Eighty-eight percent of that will be from immigration. Adding 100 million people into the U.S. creates a lot more environment issues and risks ecosystems. That’s a huge Earth Day issue.”

Beck said environmentalists almost universally opposed further immigration in the past. He pointed out that Senator Gaylord Nelson, the founder of Earth Day, once famously said: “It’s phony to say ‘I’m for the environment but not for limiting immigration.’”

Beck said that changed once prominent environmentalists aligned themselves with liberal groups for political purposes. Now, these groups only oppose population growth from natural native births.

“As long as population growth was being caused by the American people, environmental groups were against it,” Beck said. “But the American people haven’t caused population growth in decades. Immigration policy is the sole cause of long term population growth in the U.S.”

Last year, the Sierra Club’s Austin chapter pulled out of an Earth Day festival in Texas because anti-immigration groups would be in attendance.

“An awful lot of environmental groups don’t have the environment as their most important concern anymore,” Beck said. “So you have things like The Sierra Club advocating for amnesty for illegals in 2013. It was strange for The Sierra Club to take a stand on rapid increases in population in the U.S. The founders of the Sierra Club would be disturbed by that.”

“I’m a person who has a lot of interest in environmental issues and was one of the nation’s first environmental newspaper reporters back in the 1960s,” Beck said. “I can tell you that it was an essential part of the environmental movement back then. Almost every environmental group pushed it.”